1. The Field of the Invention
The present invention relates generally to speaker enclosures. More particularly, the present invention relates to speaker enclosures and methods for forming speakers which have improved sound quality.
2. State of the Art
Speakers are used in a variety of situations in order to communicate sound. They can be used as loudspeakers for public address, for movies or other events, or devices for playing music or for a host of other situations in which it is desirable to communicate sound. While there are a variety of quality levels at various sizes, it becomes increasingly difficult to produce wide dynamic range, high fidelity sound from small speakers. In fact, the smaller the speaker, the generally harder it is to get low frequencies played with high fidelity because low frequency extension benefits from large internal enclosure volume.
A speaker is typically formed with a speaker enclosure frame which forms the body of the speaker cabinet and a baffle into which the speaker driver(s) are disposed. In other words, as used herein, the enclosure frame generally relates to the back wall and sidewalls of the speaker cabinet, with the baffle forming the remaining of the cabinet.
Electrical signals sent to the speaker driver move the various parts of the speaker driver, which may include the cone, driver frame, magnetic system, front plate, rear plate, pole piece, etc., back and forth to create acoustical pressure waves. In most enclosed speakers, low frequency pressure waves generated by the speaker driver cone displacement press against walls of the speaker enclosure and tend to cause bowing or flexing. This is particularly problematic with walls which are relatively thin or which are made from materials that are less rigid. Additionally, low frequency and midrange sounds generated by the microscopic movement of the speaker driver's frame tend to be transmitted along the walls of the enclosure frame. Low frequency bowing or flexing of the enclosure walls along with their transmission of midrange sounds, creates pressure waves which interact with the pressure waves directly from the speaker driver and thereby distort the sound heard by a listener.
One known solution to vibration transfer through the enclosure frame is the use of rigid materials which, ideally, also have internal damping characteristics. For example, more than fifty years ago it was suggested to build the enclosure with bricks. Likewise damping materials, such as sand, have been used to dampen the propagation of the sound waves along and through the baffle and walls of the speaker enclosure frame. Unfortunately, such solutions are problematic, particularly when one is trying to build a small speaker. Due to size constraints, the use of bricks or other bulky materials leaves little room for the speaker itself and makes the speaker unusually heavy and volumetrically inefficient.
Another solution has been to use special materials and cross-bracing to keep flexing and transfer of sound waves to a minimum. While such materials and bracing provide a noticeable improvement in sound quality, they are also generally expensive and space consuming and result in a small speaker with disproportionate cost and reduced internal volume for bass loading.
Thus there is a need for an efficiently manufactured speaker enclosure which employs a method for reducing wall thickness while avoiding the need to use expensive, specialized materials, while also maximizing internal volume.